I know that if i was repairing a roof (example only)and found a rotten board I would be liable to fix it or let the HO get someone else to fix it. but how is the stairs connected to Jim's project?
did he raise the level of the ground? (not just bring the ground level, but raise the actual ground level there).
And if he fixed the stairs and noticed a loose board on the deck would he then have to fix that? and while he was bent down to fix the board he noticed the deck was somehow not to code or had carpenter ants..., or perhaps he didn't know at all?....I think you can see where this is going.

Just for my own edification, I'm just curious at what point you can step back and not be liable for other previous projects.